Please help me implement the following functions: C++

1 ) string add_binaries_signed(string b1, string b2) { // you implement this one fifth return "0"; }

2 ) string twos_complement(string s) { // you implement this one second return "0"; }

3 ) string signed_extension(string s) { // you implement this one first return "0"; }

4 )int binary_to_decimal_signed(string s) { // you implement this one third return 0; }